Cutlery.



ing the-characteristics a ve referred UNITED STATES PATENT OFFICE.

HARRY 3W, OF SHEFFIELD, ENGLAND.

cmsmr.

lpeoifloatlon of Letters Iatcnt.

Patented Sept. 5, 191 6 Io Drawing. Continuation of application Serial Ho. 17,858, filed larch 29, 1915. Thin application filed r larch 6, 1918. Serial No. 82,801. v

To all whom it may concern:

Be it known that I dimer Bamnwr, residing at Sheffield, orkshire, England, have invented a certain new and useful Imrovement in Cutleryi of which the followexact description.

111 is a full, clear, an

to new and useful y invention relates improvements in. cutle and polished articles 0 manufacture where non-staining properties are desired and has for its object to rovide a tempered steel cutlery blade or ot er hardened article having a polished surface and composed of an alloy which is practically untarmshable when hardened or hardened and tempered. This alloy is malleable and can be forged, rolled, hardened, tempered and polished under ordinarycommercial conditions.

The invention results from the discovery that the addition, of certain percentages of chromium and carbon to iron will produce a steel capable of t a polish and havhave discovered that the addition to iron of an amount of chromium anywhere between nine per cent. (9%) and sixteen per cent. (16%), and also an amount of carbon not greater than seven tenths r cent.

(31%) will result in a product which, when made into knife blades, has the said characteristics.

I have further found from experiments- -'that steels containin less than eight per cent. (8%) of chromium are relatively tarnis hable whatever the amount of carbon that they contain u to the limit at which they cease to be ma leableand capable of bein hardened and tempered. I have also foun that when the amount of carbon exceeds seven tenths per cent. (.7 the polished steel is tarnishable whatever the amount of chromium it may contain andjthat this con- I dition corres onds with the a pearance 1n the steel of ree carbids, whic are distinguishable microscopically on polished and etched specimens.

' A typical composition for the untarnishable steel blades embodying my invention would be as follows: carbon .80 per cent.;

manganese .30 per cent; chromium 13.0 per or other hardened cent.; iron 86.4 per cent. In producing such steel I preferably use an electric arc melting furnace. It can be readily made in such furnace. It forges easily into sheets or strips such as are required for knife blades and can be hardened and tempered by ordinary commercial processes.

Knife blades embodying my invention are made from the steel above referred to being formed, hardened and polished by rinding or bufiing in the ordinary manner, t e rodnot being a polished cutlery blade simi ar in appearance to other polished blades but possessing the remakable quality of being practically untarnishable when subjected to the ordinary uses to which knife blades are subjected because made from the alloy above described. My blades are tempered so as to be sufficiently resilient for ordinary requirements.

Small amounts, up to say one or two per cent. of nickel, copper, cobalt, tungsten, molybdenum and vanadium a ear to be without influence on the untarnls able propertf' of the steel.

n practice it is best 'not to attempt to obtain an alloy containing above 4% of carbon, but rather to try to obtain an alloy containing an amount of carbon less than 4% thus leaving a wider margin for variations from the alloy sought to. be produced since the desired result is attained when considerably less carbon is present.

This application is a continuation of m application Serial No. 17,856, filed Marc 29th 1915., y

' As is evident to those skilled, in the art, my invention permits of various modifications without departing from the spirit thereof or the scope of the appended claims.

What I claim is,

1. A hardened and polished article of manufacture composed of a ferrous alloy containing between nine per cent. (9%) and sixteen per cent. (16%) of chromium and carbon in quantity less than seven tenths per cent. (17%).

2. A hardened, tern ered and polished cutlery blade compose of a ferrous alloy containing between nine per cent. (9%) and sixteen per cent. (16%) of chromium and carbon in quantity less than seven tenths per cent. (.7%), and not containing any microscopically distinguishable free carbids.

3. A hardened and polished cutlery article composed of a ferrous alloy containing be tween nine per cent. (9%) and sixteen per cent. (16%) of chromium and carbon in quantity less than six tenths per cent. (5%).

4. A hardened and polished article of 10 manufacture composed of a ferrous alloy containing approximately carbon 0.30% manganese 0.30% and chromium 13.0%.

HARRY BREARLEY. 

